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Frontiers in Optics

Temperature-insensitive robust source of high-quality polarization-entanglement

Nilesh Tiwari, Omshankar, Vivek Venkataraman, Joyee Ghosh

Published Jan 1, 2025• 0 citations
Publisher

Abstract

We demonstrate a temperature-robust Sagnac-interferometer based source of polarization-entangled photons using 20-mm long ppKTP, maintaining stable operation with > 92% fidelity, over > 1.2 ◦ C change.
DOI
10.1364/fio.2025.jd1a.67

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We demonstrate a wavelength-tunable, fiber-coupled source of polarization- entangled photons with extremely high spectral brightness and quality of entanglement. Using a 25 mm PPKTP crystal inside a polarization Sagnac interferometer we detect a spectral brightness of 273000 pairs (s mW nm)(-1), a factor of 28 better than comparable previous sources while state tomography showed the two-photon state to have a tangle of T = 0.987. This improvement was achieved by use of a long crystal, careful selection of focusing parameters and single-mode fiber coupling. We demonstrate that, due to the particular geometry of the setup, the signal and idler wavelengths can be tuned over a wide range without loss of entanglement.
We demonstrate a wavelength-tunable, fiber-coupled source of polarization-entangled photons with extremely high spectral brightness and quality of entanglement. Using a 25 mm PPKTP crystal inside a polarization Sagnac interferometer we detect a spectral brightness of 273000 pairs/(s mW nm), a factor of 28 better than comparable previous sources while state tomography showed the two-photon state to have a tangle of T=0.987. This improvement was achieved by use of a long crystal, careful selection of focusing parameters and single-mode fiber coupling. We demonstrate that, due to the particular geometry of the setup, the signal and idler wavelengths can be tuned over a wide range without loss of entanglement.